This invention is directed to air freshening devices of the type suitable for use in domestic environments. The invention is further directed to a method for freshening ambient air in such environments.
It is known to provide air freshening devices which slowly release a fragrance into the atmosphere in order to avoid or mask unpleasant odors. Such air freshening devices may comprise a gel-like matrix containing one or more fragrance components. The matrix includes an emanating surface from which the fragrance evaporates on contact with the air. However, such conventional air freshening devices suffer from the disadvantage that the concentration of the fragrance component or components remaining within the matrix decreases with time and a concentration gradient thus forms across the matrix. Thus, as time passes, the emanating surface contains less fragrance and the rate of fragrance emanation decreases. The user of the air freshening device then perceives that the air freshening device is less efficient as time progresses.
An alternative type of air freshening device comprises a liquid in a container provided with a wick into which liquid can be drawn by capillary action. The volatile liquid can evaporate from the exposed end of the wick. As the level of liquid in the container falls, the liquid must travel a greater distance up the wick before it can evaporate. As a result, it is difficult to obtain a uniform release of fragrance over time.
It would be desirable to develop a fragrance emanating system which overcomes the above disadvantages.
Accordingly, the present invention provides a fragrance emanating device for freshening atmospheric air, which device comprises:
(i) a closed container for accommodating a liquid fragrance composition,
(ii) an emanator having a surface open to the atmosphere (ambient air) for evaporation of the liquid fragrance composition, and
(iii) a conduit linking the container and the emanator surface.
The arrangement of the components of the device is such that, in use, thermal expansion of the air and/or liquid in the container, resulting from an increase in temperature, causes the fragrance composition to travel along the conduit from the container to the emanating surface of the emanator, and thermal contraction of the air and/or liquid in the container, resulting from a decrease in temperature, causes air from the atmosphere to enter the container via the conduit.
Using the air freshening device of the present invention, a fresh supply of the fragrance composition is fed to the emanating surface with each temperature increase and temperature decrease cycle. Thus, there is no gradual diminution in the rate of emanation with time.
In a particularly preferred embodiment, the container includes a base at one end to enable the device to be supported on a level surface and, at its other end, it includes an emanator having a dished emanator surface. The conduit connecting the container and the emanator may be in the form of a dip tube, generally vertically disposed within the interior of the container, and extending between the emanating surface and the base of the container. By suitable selection of the volume of the container, the volume of the conduit and the diameter thereof, it can be ensured that the thermal expansion and contraction occurring with daily changes in the temperature of the air cause fragrance composition to be expelled from the container to the emanating surface and air to be drawn into the container from the atmosphere to replace the expelled fragrance.
If appropriate, the container may be suitably thermally insulated in order to achieve the desired daily range of temperature variation.
In one embodiment of the present invention, the container is only partially filled with the fragrance composition, so that it also contains atmospheric air. In this case, it is primarily the expansion of the air above the surface of the fragrance composition with temperature change which results in the desired expulsion of the fragrance composition from the container. Alternatively, the container may initially be completely filled with fragrance composition, in which case the thermal expansion of the fragrance composition itself provides the driving force for expelling the fragrance composition from the container. Alternatively, the device may be primed by removal of an initial charge of liquid, for example, applying pressure to a flexible container which is full of the fragrance composition. As time passes, air will be drawn into the container and the expansion and contraction of the air will then contribute to the expulsion of fragrance composition in subsequent temperature cycles.
In another embodiment, the driving force is derived from the liquid only. In this case the device includes a reservoir to top up the container with liquid as fragrance composition is removed and a means is provided for removing the air which enters the container from the atmosphere during cooling. The control of liquid flow and air removal may include various valve arrangements.
In one form of this embodiment, the container may include another liquid, in addition to the liquid fragrance composition. This other liquid may be a liquid (such as ethanol) miscible with the liquid fragrance composition or a liquid which is immiscible (such as water or a perfluoroether) with the liquid fragrance composition. This other liquid similarly provides the driving force for expelling the fragrance from the container due to its thermal expansion and contraction.
The container may be formed, for example, of plastic materials, glass, ceramic, pottery or metal, the prime requirement being to contain the liquid fragrance composition and the air in a manner such that expansion can only occur up the dip tube.
The emanator may be formed from a porous material, which may be treated so as to make it hydrophobic or lipophobic, as appropriate. Suitable porous materials include ceramics or earthenware, plastic materials, paper, cellulose wadding, and finely divided mineral particles, such as silica, alumina or carbon. The emanator may be in the form of a flat plate or a film, planar or curviform, and may be wholly formed from the porous material or may be a composite of porous and non-porous materials.